Explain Doctrine of Signatures?

Handed down from the ancients, and elaborated on by the herbalists, was the 'Doctrine of Signatures', which was based on features that resembled portions of the human body, must have been so created for the purpose of-furnishing remedies for the ailments of those portions of the body. Many plants were given common names that referred to supposed remedial properties, and the origin of many scientific names that are still in use today may be traced to this doctrine. For example, the generic name Hepatica, the shape of the leaves in that genus being thought to resemble the shape of the liver, and the leaves, therefore, to be a remedy for diseases of that organ.